Attack and decay circuitry for electronic musical instrument

ABSTRACT

A switching circuit for an electronic musical instrument which is generally composed of an emitter-grounded type transistor amplifier in which an input is supplied to a base, an output is taken out from a collector and a key switch is interposed in an emitter path. The emitter is connected serially through a first resistor, a second resistor, a first diode, and the key switch to a power line. A juncture between the first and second resistors is connected to a cutoff potential via a third resistor and to the power line via a first capacitor for giving a decay effect. The emitter is further connected serially through a second diode, a second capacitor and a fourth resistor, to a juncture between the first diode and the key switch for giving an attack effect.

United States Patent [72] inventor Takeshi Adachi Shizuoka-ken, Japan [21] Appl. No. 826,490 [22] Filed May 21, 1969 [45] Patented July 6, 1971 [73] Assignee Nippon Gakki Seizo Kabushiki Kalsha Shizuoka-ken, Japan [54] ATTACK AND DECAY CIRCUITRY FOR ELECTRONIC MUSICAL INSTRUMENT 3 Claims, 5 Drawing Figs. [52] 11.8. Cl 84/126, 84/113 [51] Int. Cl Gl0h 1/02 [50) Field oiSearch 84/l.13, 1.26

[56] References Cited UNITED STATES PATENTS 3,l4l,9l9 7/1964 Mabuchi 84/1 .26

3,288,907 11/1966 George Primary ExaminerD. F. Duggan Assistant Examiner-U. Weldon Attorney-Holman and Stern ABSTRACT: A switching circuit for an electronic musical instrument which is generally composed of an emitter-grounded type transistor amplifier in which an input is supplied to a base, an output is taken out from a collector and a key switch is interposed in an emitter path. The emitter is connected serially through a first resistor, a second resistor, a first diode, and the key switch to a power line. A juncture between the first and second resistors is connected to a cutoff potential via a third resistor and to the power line via a first capacitor for giving a decay effect. The emitter is further connected serially through a second diode, a second capacitor and a fourth resistor, to a juncture between the first diode and the key switch for giving an attack effect.

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-- TIME INVENTOR 77mm 604ml BY 2.44M. MA 1 ATTORNEY 6 ATTACK AND DECAY CIRCUITRY FOR ELECTRONIC MUSICAL INSTRUMENT BACKGROUND OF THE INVENTION This invention relates to switching circuits employed in electronic musical instruments and more particularly to a type of switching circuit whereby either of the rise time and output signal level during the rise time can be regulated, and a socalled attack efiect in the signal is thereby obtained. Heretofore, in an electronic musical instrument, a switching system using a transistor keyer has been widely used for obtaining the gradual rise of a tone signal which prevents the occurrence of unpleasant clicks during the rise time, and rendering the gradual decay of the tone signal which gives a sustain effect (as in the damping tone of a piano). This system employs a number of separate switching circuits operable from corresponding key switches on a keyboard.

. An example of such a keyer of switching circuit and an operational characteristic thereof are shown in FIGS. I and 3 of the accompanying drawing, which will be described in more detail hereinafter. As is apparent from FIG. I, a signal entering the input terminal 1 of an emitter-grounded-type amplifier circuit is passed through the amplifying circuit along with open-and-closing operation of a key switch 3 inserted in series with an emitter resistor Re, and an output signal is obtained from the output terminal 2 of the switching circuit. At this time, the rise time of the envelope of the signal is determined by a time constant which is determined by the magnitudes of a resistor R and a capacitor C, shown in the drawing, and the decay time (attenuation time) of the envelope is determined by the capacitor C, resistors 8, 9, and partly by a variable resistor 11.

An amplitude-time characteristic of the indirect switching circuit is shown in FIG. 3. When a key switch is depressed, the

tone signal starts to pass through the switching circuit. After a rise time represented by t,,-t,, which ordinarily is about 10 ms., the tone signal is saturated into a constant value, and for a period represented by t,t a tone signal of constant am-.

plitude is delivered from the output terminal. When the key is released, the amplitude of the tone signal continuously decreases for a period of -1 until at last the output signal vanishes at the instant of 1 The decay time or attenuation time 1 -1 which corresponds to a short sustain time characteristic of the switching circuit, is about 100 ms., and the decay time of t -t,,, which corresponds to a longer sustain time characteristic of the same, may be about 1 sec.

Although the switching circuit as described above may have superior features such as elimination of unpleasant click sounds or provision of sustain effect, such a circuit is inconvenient for rendition of music including chords of numerous tones or music ofquick tempo.

The traditional musical instruments such as a piano, guitar, harp, and percussion instruments have a characteristic tone curve as shown in FIG. 4. It will be seen that the tone rises sharply to its maximum level and thereafter decays gradually. Because of such configuration of the tone curve, there is no possibility of individual tones being indistinguishable from each other.

SUMMARY OF THE INVENTION Therefore, a principal object of the present invention is to provide a novel construction of a switching circuit which can produce a sharply rising tone having a significant attack" effect as is obtainable from the traditional musical instruments and, at the same time, possesses the above described advantageous features of the conventional switching circuit.

Another object of the invention is to provide a novel type of switching circuit whereby the magnitude of the peak value of the sharply rising tone signal can be varied at will.

These and other objects of the present invention can be achieved by a novel type of switching circuit including a transistor, the base of which is connected to the input terminal of the switching circuit, the collector of which is connected to the output terminal, and the emitter of which is connected to a emitter resistor, a capacitor, charging and discharging resistor circuits for the capacitor, and a key switch and having the improvement comprising a diode connected in series with the resistor of the discharge resistor circuit and conducting the discharge current from the capacitor, a bypass circuit consisting of another diode, a second capacitor, and a resistor, connected in series, and provided between the emitter and the key switch, a charging circuit for the second capacitor, the charging voltage of which is adjustable, whereby the rising characteristic of the output signal is made controllable by varying the charging voltage of the second capacitor. 1 The invention will be better understood from the following description with respect to a preferred embodiment thereof when read in conjunction with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a diagram showing a switching circuit employed in conventional electronic musical instruments;

FIG. 2 is a diagram showing a switching circuit according to the present invention;

FIG. 3 is a graphical representation of a tone level variation relative to time in conventional switching circuit;

FIG. 4 is another graphical representation of a natural tone such as that from a piano, guitar, harp, or the like, relative to time; and

FIG. 5 is a similar graphical representation of the tone level variation relative to time obtained in a switching circuit ac cording to the present invention.

DETAILED DESCRIPTION The switching circuit according to the present invention will now be described in detail with reference made to FIG. 2. As is shown in FIG. 2, a main characteristic feature of the present invention resides in the provision of diodes I2, 13, a capacitor 14 and a resistor 15 all connected in the emitter circuit in addition to the conventional construction as shown in FIG. I. Resistors I6, 17 and 18 are provided to achieve further improvement. Among the above described resistors, the variable resistor 17 is not necessarily provided in each of the switching circuits but may be provided singly for the whole musical instrument.

A power source 5 of, for instance, 9v. and another power source 6 of, for instance, 3v. are provided as shown in FIG. 2. With the positive side of the power source 5 grounded, a potential of 9v. is obtained at the junction point 7.

With the key switch 3 in opened condition, the capacitor C is in the charged state due to a current flowing from the power source 6 through the resistors 8 and 9, and the potential of the junction point B becomes high, which in turn raises the emitter potential, whereby the transistor 4 is brought into the cutoff condition. The potential of the junction point C is elevated to a value equivalent to that of the contactor 19 of the variable resistor 17.

Whenever the key switch 3 is closed, the potential at the junction point B is gradually lowered with the time constant CR until a potential of -12v. is attained as in the case of the conventional switching circuit as shown in FIG. 1. However, in FIG. 2, the potential of the junction point C is abruptly decreased from the potential of the standstill condition as described above by an amount corresponding to the voltage change (decrease) of the junction point D (about 3v. from 9v. to l2v.) and thereafter gradually raised to the potential of the junction point 19 with a time constant determined by the resistors l5, l6 and the capacitor 14. During the abovementioned variation of the potential, the diode l3 conducts for a period during which the potential of the junction point C is lower than that of the emitter (the potential at the junction point E), whereby the emitter resistor Re is bypassed through a bypass circuit including the diode l3. Bypassing of the emitter resistor Re increases in turn the collector current of the transistor 4 to increase the amplifier gain, and a high-intensity signal is obtained at the output terminal 2. The prominent portion a of FIG. 5 illustrates the above-described feature of the operation.

Subsequently, when the potential of the junction point C rises higher than the emitter potential of the transistor 4, the diode 13 is shifted'to its nonconductive state, and the output 'signal is brought into the stationary amplitude state as indicated by the portion b of FIG. 5.

When the key switch 3 is opened again, the diodes 12, 13 are both kept in the nonconductive state, and, therefore, the output signal is gradually atteruiated as shown by the portion c or d in FIG. 5 due to charging of the capacitor C depending on the position of the variable resistor 11. The capacitor 14, on the other hand, is discharged through the resistors l5, l8 and returns to the original condition.

Here, if the standstill potential of the junction point C (that is, the charged potential of the capacitor 14 when the key switch 3 is in the open state) is adjusted by varying the potential of the junction point 19 of the variable resistor 17, the extent to which the potential of the junction point C becomes lower than the potential of the emitter E at the time the key switch 3 is closed can be adjusted, whereby the level and the duration of the portion a of FIG. 5 can be varied at will.

Because the switching circuit according to the present invention provides a quick rise or fast attack of the signal with a slow decay maintained at a necessary time length and in addisister, and first unidirectional element and a key switch connected in series circuit between'said emitter and said power source; a third resistor connected between a juncture of said first and second resistors and a potential point which gives said emitter a voltage rendering the transistor cutoff; a first capacitor connected between said juncture of said first and second resistors and said power source; and a second unidirectional element, a second capacitor and a fourth resistor connection in series circuit between said emitter and a juncture of said first unidirectional element and said key switch.

2. An attack and decay circuit as defined in claim 1, wherein there is further provided a charging circuit connected across said second capacitor and having a variable voltage.

3. An attack and decay circuit as set forth in claim 1, wherein said first and second unidirectional elements are diodes. 

1. An attack and decay circuit for an electronic musical instrument, said circuit comprising an input terminal and an output terminal; a power source; a transistor having a base connected to said input terminal, a collector connected to said output terminal, and an emitter; a first resistor, a second resistor, and first unidirectional element and a key switch connected in series circuit between said emitter and said power source; a third resistor connected between a juncture of said first and second resistors and a potential point which gives said emitter a voltage rendering the transistor cutoff; a fiRst capacitor connected between said juncture of said first and second resistors and said power source; and a second unidirectional element, a second capacitor and a fourth resistor connection in series circuit between said emitter and a juncture of said first unidirectional element and said key switch.
 2. An attack and decay circuit as defined in claim 1, wherein there is further provided a charging circuit connected across said second capacitor and having a variable voltage.
 3. An attack and decay circuit as set forth in claim 1, wherein said first and second unidirectional elements are diodes. 